Tritium (3H or T) is the radioactive isotope of hydrogen and for over fifty years it has been extensively used to radiolabel numerous molecules of interest to biologists. Among its many uses, tritium offers significant advantages as a molecular tag. First, tritium is essentially the same size as hydrogen, and therefore, causes no significant structural change to the radiolabelled molecule of interest. Also, the half life of tritium is a convenient 12.3 years, which allows (if necessary) for long complex multistep syntheses as well as a reasonable shelf life of the tritiated product. Also, over the course of several decades, numerous synthetic methods have been discovered to install it into molecules at high specific activity. Tritium will likely be the isotope of choice to radiolabel many interesting substances for many years to come.
Unfortunately, during the course of using tritium for radiolabelling, there is an almost unavoidable consequence of creating unwanted tritiated byproducts. In many instances, this occurs because tritium gas can catalytically exchange with hydrogen attached to heteroatoms (oxygen, nitrogen, sulfur etc.) and then back exchange with protons during protic solvent work-up of the reaction, creating tritiated byproduct. These tritiated byproducts are often complicated mixtures of diverse chemicals and of too low specific activity to be useful for any radiolabelling reactions. Importantly, this tritiated byproduct is very costly to dispose of and, since many of the byproducts are low boiling solvents, there are also a storage safety concerns and possible contamination risks prior to disposal.
Clearly, complex mixtures of tritiated byproducts entering the environment are a concern. As such, there is an unmet technical need for processes and systems to recycle these low specific activity materials to pure high specific activity tritium gas.